1. Field of the Invention
The present invention relates to a route setting method of and a route setting apparatus for setting a route so as to speedily reach a destination set in advance, for use in a navigation system.
2. Description of the Related Art
There is a so-called navigation apparatus, which displays a map including a position where a movable body in various kinds such as an automobile, an airplane, a ship etc., is currently located, and further superimposes a position mark indicating a position of the movable body at the currently located position on the displayed map, so as to perform a route guidance or navigation to the destination on the basis of the display. Among the navigation apparatuses, as on-vehicle navigation apparatuses which are mounted on vehicles or auto-mobiles, there is a self-sustained or built-in type navigation apparatus and a GPS (Global Positioning System) type navigation apparatus as rough categories.
The former is a navigation apparatus, which obtains a moving direction and a moving distance of the movable body by use of a speed sensor, an angular speed sensor etc. equipped in or built in the pertinent vehicle, adds them with respect to a standard position so as to calculate the present position, and displays the present position mark and the corresponding map on the display picture plane on the basis of the calculated present position.
On the other hand, the latter is a navigation apparatus, which receives electric waves from a plurality of GPS satellites launched in the space, calculates the present position of the movable body by means of a 3-dimensional measuring method or a 2-dimensional measuring method on the basis of the electric wave reception results, and displays the present position mark and the corresponding map on the display picture plane on the basis of the calculated present position.
Further, there is an on-vehicle navigation apparatus provided with both functions of the above described self-sustained type and GPS type.
According to the above explained navigation apparatus, since the user (e.g. the driver) can grasp the present position of the self vehicle and the map in the vicinity of the present position in association with each other, it is possible to reach a destination without losing his or her way even in an area where the user has never experienced.
Further, the on-vehicle navigation apparatus may have a so-called route setting function to calculate, when an original departure point and a final destination point are inputted by the user in advance, the shortest route including a plurality of route points from the original departure point to the final destination point on the basis of these inputted points, and to superimpose the calculated shortest route on the map displayed on the picture plane.
However, in the above explained route setting function, it may happen a case that the most convenient route for the user cannot bealways calculated ordisplayedas various traffic regulations such as one way traffic etc. and the road grids become complicated, which is a problem.
For example, when the movable body is deviated from the set shortest route for some reason, as a first method according to the above mentioned route setting function, a predetermined process area around the present position of the movable body as a center is set. Then, the route point, which is the closest to the present position of the movable body among the set route points within the predetermined process area, is searched, and the route is set again from the present position of the movable body so as to return or recover to the set shortest route via this searched route point. On the other hand, as a second method according to the above mentioned route setting function, setting of the shortest route itself from the present position of the movable body to the final destination point is performed again.
However, according to the above mentioned first method to recover from the deviation, in case that the distance from the route point, which is the closest to the present position of the movable body, to the final destination point is longer than the distance from the present position of the movable body to the final destination point, if the movable body is recovered onto the set shortest route via the searched route point, which is the closest to the present position of the movable body, the newly set route becomes a detour as the route to the final destination point, which is a problem. Further, according to the above mentioned second method to recover from the deviation, in case that the distance from the present position of the movable body to the final destination point is rather long, it takes a relatively long time duration to newly set the shortest route, and the movable body cannot be moved during that time duration, which is another problem. In summary, when the movable body is deviated from the shortest route, there is such a problem that the arrival to the final destination point is considerably delayed as a result of these, according to the above explained route setting function
On the other hand, according to the above explained route setting function, in case that the user intends to return to the original departure point in the middle of traveling on the set shortest route, the original departure point and the final destination point on the set shortest route are simply reverted to each other. And that, the route order of the route points along the set shortest route are also reverted, and the advance direction is also reverted while the set shortest route itself is not changed. However, because of a traffic regulations such as one way traffic etc. and a new traffic jam due to the reversion of the advance direction etc., it may happen a case that this reverted originally set shortest route is not the shortest route anymore to return fastest to the original departure point, which is another problem.